PCI-SIG announces 8GT/s transfer rate for PCIe 3.0

PCI-SIG announced the finalization of the transfer rate for the upcoming PCIe …

The PCI-SIG (Special Interest Group), which controls the PCI spec, announced the finalization of the transfer rate for the upcoming PCI-Express 3.0 specification, currently expected to debut in late 2009 or 2010. PCIe 3.0 will transfer data at a rate of 8GT/s, but unlike PCIe 2.0 or PCIe 1.1, will not require devices to pay a 20 percent bandwidth overhead cost.

Up until now, PCI-SIG has used GT/s as a unit of measurement for PCIe bandwidth, rather than the more familiar Gb/s. GT stands for GigaTransfers per second, and differs from the standard unit of measurement due to PCI-Express' 8bit/10bit encoding system. Put simply, PCIe 1.1 and 2.0 use 10 bits of encoding to send 8 bits of data. This, in turn, results in theoretical peak transfer rates that are only 80 percent as fast as the number typically expressed by the group in GigaTransfers per Second.

A PCIe 1.1-compliant system has a peak transfer rate of 2.5GT/s or 2Gbps/s. PCIe 2.0 doubles this to 5GT/s or 4Gb/s. PCIe 3.0 will increase the transfer rate from 5 GT/s in PCIe 2.0 to 8 GT/s, but as we've previously stated, will not require the same encoding mechanism. PCIe 3.0 will therefore still double total available bandwidth as compared to PCIe 2.0.

Hopefully we'll start to see more widespread use of all this additional bandwidth in the form of more PCIe-compliant peripherals. While the interface is proving popular in the server market, and has obviously grown to dominate the video card industry, a number of other peripherals have maintained a steadfast presence on good ol' PCI. One potential benefit to PCIe 3.0 would be the ability to build higher-end graphics cards that require a smaller PCIe slot to interface with the board. This, in turn, could open up new markets for higher-end graphics capability in system form factors that are currently too small to use large x8 or x16 slots.

There are still a number of steps that need to be taken before PCIe 3.0 becomes available, and PCIe 2.0 isn't exactly widespread either. The PCI-SIG expects PCIe 2.0 to be in wide availability by the end of this year, with PCIe 3.0 following by 2010.